"I am a thinking thing, a substance whose whole essence or nature consists in thinking, and there is no need of any place, nor does it depend on any material thing."

"All that is solid melts into air."

"The two operations of our understanding, intuition and deduction, on which alone we have said we must rely in the acquisition of knowledge."

"The preservation of health has always been the principal end of my studies."

"Whenever anyone has offended me, I try to raise my soul so high that the offense cannot reach it."